The present invention relates to novel ultra high affinity neutralizing antibodies.
The current incidence of infection caused by resistant or difficult to control microbes has created a need for newer approaches to controlling such organisms, as well as to treating those already infected.
Among the more difficult infectious agents to control and treat are the viruses. For example, respiratory syncytial virus (RSV) is the major cause of acute respiratory illness in young children admitted to hospitals and the major cause of lower respiratory tract infection in young children. A major obstacle to producing an effective vaccine against such agents as RSV has been the issue of safety. Conversely, the use of immunoglobulins against such viral agents has proven of some value. For example, studies have shown that high-titred RSV immunoglobulin was effective both in prophylaxis and therapy for RSV infections in animal models.
An alternative approach has been the development of antibodies, especially neutralizing monoclonal antibodies, with high specific neutralizing activity. One drawback to this route has been the need to produce human antibodies rather than those of mouse or rat and thus minimize the development of human anti-mouse or anti-rat antibody responses, which potentially results in further immune pathology.
An alternative approach has been the production of human-murine chimeric antibodies in which the genes encoding the mouse heavy and light chain variable regions have been coupled to the genes for human heavy and light chain constant regions to produce chimeric, or hybrid, antibodies.
In some cases, mouse CDRs have been grafted onto human constant and framework regions with some of the mouse framework amino acids being substituted for correspondingly positioned human amino acids to provide a “humanized” antibody. [Queen, U.S. Pat. Nos. 5,693,761 and 5,693,762]. However, such antibodies contain intact mouse CDR regions and have met with mixed effectiveness, producing affinities often no higher than 107 to 108 M−1.
A humanized anti-RSV antibody with good affinity has been prepared and is currently being marketed. [See: Johnson, U.S. Pat. No. 5,824,307]
The production of ultra high affinity antibodies would be desirable from the point of view of both the neutralizing ability of such an antibody as well as from the more practical aspects of needing to produce less antibody in order to achieve a desirable degree of clinical effectiveness, thereby cutting costs of production and/or allowing a greater degree of clinical effectiveness for administration in the same volume.